Thermal operated circuit controlling device



0. S. FIELD THERMAL OPERATED CIRCUIT CONTROLLING DEVICE Filed Aug. 15, 1934 FIG. 3.

wm m INVENTOR 0. 5 9

ATTORNEY Feb. 22, 1938.

Patented Feb. 22 1938 THERMAL OPERATED CIRCUIT CONTROL- LING DEVICE Oscar S. Field, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application August 15, 1934, Serial No. 739,981

1 Claims. (Cl. 200-122) This invention relates to circuit controlling devices of the thermal element type. The heating and cooling of bi-metallic thermal elements in response to the flow and interruption of electric current may be advantageously employed to open or close contacts on a time interval basis. In the interests of economy and efficiency, such thermal elements may be enclosed in an evacuated or gas filled bulb, as disclosed for example, in my Patent 2,035,426, granted March 24, 1936, on application, Ser. No. 634,019, filed September 20, 1932.

In accordance with this invention, generally speaking, it is proposed to provide for the ready adjustment of the time 01' operation of such enclosed thermal elements by varying the rate at which heat may be conducted or radiated from the heating element, either by changing the pressure of the gas in the enclosing bulb, or by changing the area exposed to the external air of a heat conducting member extending into the bulb into contact with the thermal element.

The various characteristic features, advantages, and attributes of the invention will be in part apparent, and in part pointed out as the description progresses.

The accompanying drawing illustrates in. a simplif ed and diagrammatic manner certain speclflc embodiments of the invention. Fig. 1 shows the structureof an enclosed thermal element having provision for adjusting the time of its operation by varying the pressure of the gas iri the enclosed bulb. Fig. 2 is a fragmentary view illustrating the application of a heat conducting part to an enclosed thermal element device for varying its time of operation; and Fig. 3 is another fragmentary view illustrating a modification of the heat conducting part.

Referring to Fig. 1, the thermal device comprises a bimetallic strip. lot the usual type and construction, such as brass and- Invar" strips fastened together. This member i is anchored at its lower end in the stem oi a glass tube or bulb B,'in the usual'way and in accordance with well-= known practice. A similar bi-metallic strip 2 is welded or otherwise rigidly fastened to the upper end of strip I; and the two strips i and 2 are disposed in an opposing relation, so that they will be deformed in opposite .directlons by a change in the temperature of both, thereby maintaining the upper end of the two strips in substantially the same position witli relation to the. lower end, so as to compensate for gradual changes in ambient temperature. The lower strip i is heated by a coil or filament I of suitable resistance wire in the usual way, one end of this heating coil being soldered or welded to an anchor member 4 in the stem of the bulb B. I

In the arrangement shown, two resilient contact members 5 and 6 are anchored at their lower ends in the stem of the bulb B, and are connected together at the upper ends and to the bi-metallic strip 2 by a tie-piece or driver member 1 of suitable insulating material, such as mica. Stationary contact members 8, 8', and ill of similar construction are anchored at their lower ends to engage the contact members 5 and 6. These contact members may be made as a whole of suitable contact material, such as a nickel alloy; or contact pieces may be attached to these members at the points of contact. One end of the heating coil 3 is connected to the contact member 5.

The arrangement .of contacts illustrated is merely typical; and the contact members may. be arranged to open or close contacts in the heated or cooled condition of the thermal strip i.

The contact members and the anchor member 4 for the heating coil are connected by wires to pins ii in an insulating base C, attached to the glass bulb or container B in accordance with regular practice. r

In the embodiment of the invention illustrated in Fig. 1, a flexible metallic diaphragm l2 of bronze or other suitable material, preferably corrugated, is attached to the upper end of the glass bulb B, the edgeof this diaphragm forming a gas-tight seal with the glass. An adjusting nut it in a bracket or stirrup i4 suitably secured to the base C, is arranged to deform the diaphragm l2. After the parts have been assembled in the glass tube B and the tube is evacuated in accordance with the usual practice, it is preferably filled with inert gas such as argon or nitrogen, to a pressure conforming with the time characteristics desired.

When electric current is supplied to the heating coil 3, the temperature of the lower bi-metallic strip i is raised relative to that of the upper strip 2. Consequently, the upper end of the two strips is moved or displaced. This movement is assumed to be to the left to open contacts 8-! and 5-H, and to close contacts 5-8. The time taken to raise the temperature of the strip l sufflciently to cause the necessary displacement to operate these contacts seems to depend on the rate at which heat may be conducted or dissipated, as well as the rate at which the heat is supplied. Experiments indicate that the rate at which the heat is dissipated from the thermal strip l is due to a large extent to conduction through the gas in the tum; and it has been found, that by varying the pressure of this gas, the rate of dissipation of the heat may be materially changed so as to increase or decrease within certain limits the time required to operate the contacts for the same heating current. Accordingly, this invention contemplates the pro vision of the diaphragm i2, or equivalent means, by which the pressure of gas within the tube can be readily varied after the device has been assembled, for the purpose of adjusting the operating time of thermal operated circuit controllers, either to give the same time for a group of like devices in spite of manufacturing variations, or to adjust the same device for different operating times for different applications.

Fig. 2 illustrates another construction in which a heat conducting member i5 is welded or otherwise suitably iastenedto the lower iii-metallic strip i, anciis sealed in the glass bulb B with its outer end exposed to the atmosphere. It is contemplated that after assembly and test or the device, the area of the member to exposed to the external air may be changed by cutting it ed to diilerent lengths; and in this way'the rate of disnpation 01' heat irom the strip i may be var led to obtain the desired adjustment in operating time. This construction may be used with evacuated bulbs, as well as gas filled bulbs.

Fig. 3 illustrates a. modification in the structure of the heat dissipating member 95 whichis bent or shaped at its outer end tor the attach ment by a screw or the like of radiating disc or piece M the size and area of which can be selected to give the desired exposure and radiation to the atmosphere.

The specific embodiments of the invention shown are merely illustrative; and various adaptstions, modifications, and additions may be made to the specific constructions shown and described, without departing from the invention.

What I claim is:

l. A thermally operated circuit controlling de vice comprising a lei-metallic thermal element in an enclosing bulb, means for heating said element, contacts operated by deformation of said element, and means for varying the rate oi dissipation of heat from said element.

2. A thermally operated circuit controliins olevice of the character described, comprising it lolmetallic strip enclosed in Eflh fiilid tube, and means adapted to be adjusted after assembly oi the device for varying the pressure of the has in saidtube, and thereby change the rate of iii-i slpation oi heat irom said bi=metallic strip.

3. A thermally operated circuit controller comprising a bi-metallic strip within an enclosing bulb, means for supplyingheat to said strip, heat conducting means connected to said strip and extending outside oi said bulb, said heat conducting means being adapted to have its exposed area changed to vary the rate oi dissipation of heat from said strip.

4. A thermally operated circuit controller comprising two bhmetallic strips mechanically connected and disposed to be deformed in opposite directions by a change in'the temperature of looth, means for heating one of said strips independently oi the other, contacts operated by the deformation 0! said heated strip, a gas-tight bulb enclosing said strips and said contacts, and means changeable after assembly of the device, for varying the rate of dissipation oi" heat from the heated strip, said means for heating said strips being electrical heating means having connections extending outside of said bulb, whereby the time required to operate said contacts after application of current to said heating means can lie-regulated and be substantially constant irrespective of ambient temperatures.

5. A thermal circuit controlling devicecomprising, a bi-metallic strip, means for heating the strip, a closed flexible gas filled chamber enclosing the strip, and meansaccessible from the outside oi the chamber for varying the size of the chamber and thus veil '13 the pressure of the gas therein, whereby to change the rate of dissipation 01' heat Irons the bi-metallic strip.

6. A thermal circuit controlling device comprising, a lei-metallic strip, means for heating the strip, a closed flexible gas filled chamber enclosing the strip, a closed rigid casing enclosing the chamber, and means accessible from the outside oi the casingj for varying the size of the chamber and thus varying the pressure of the as therein, whereby "to change the rate of disslpation 0! heat from the bl-nietallic strip.

l. A thermally operated circuit controller comprising a iii-metallic strip within an enclosing hulls, means for supplying heat to said strip, heat conducting means connected to said strip and extending outside of said bulb, said heat conducting means having receiving and fastening means thereon for holding heat radiating memhers oi various radiating capacities, whereby to' vary the rate of dissipation oi heat by said strip.

i'JfiCAR S. FIELD. 

